1. Field of the Invention
This invention relates to the fields of porcelain, ceramic and stoneware manufacturing and processing and more particularly to a cleaning composition and method for reducing fine silica dust from becoming air-borne during such processing.
2. Art Background
In the manufacture of porcelain, ceramic and stoneware products, a slurry is poured into a mold, and thereafter allowed to dry. The dried product, often termed "greenware" is then further processed or cleaned wherein it is smoothed and shaped. During this smoothing and shaping process, dust from the dried slurry escaped in the air. This dust includes powdered silica. Porcelain contains about 20% silica, and 3 to 5% of the porcelain is fine crystalline silica, a material which has been recognized as being dangerous. The other materials also contain significant amounts of fine crystalline silica as well.
Specifically, particles of crystalline silica, often called fine crystalline silica which are airborne and less than 3.5 microns are considered to be dangerous. Particles greater than 3.5 microns are considered only a nuisance since they can be naturally expelled from the lungs. Those particles which are in the range of 3.5 microns down to 1 micron may be inhaled and may become lodged in the lungs. They are too small to be evacuated by coughing, so they remain on the surface of the lung cells and cause scar tissue to form thereover, resulting in silicosis, a form of a disabling, progressive and sometimes fatal pulmonary fibrosis characterized by the presence of nodulation in the lungs. Particles less than 1 micron in size pass through the lungs and into the bloodstream, and eventually settles in the eye, resulting in impaired vision and eventually blindness.
OSHA has recognized the hazards of fine crystalline silica and has promulgated regulations relating to fine crystalline silica in September, 1978. However, OSHA regulations only apply to commercial establishments employing 10 employees or more. On the other hand, much of the porcelain, and a significant amount of the stoneware and ceramic work in this country is performed by hobbyists and by small establishments of fewer than 10 employees, thereby rendering the OSHA requirements moot for the majority of craftspersons in the field. In any event, as explained more fully below, no effective prior art method has heretofore been established which does not have serious drawbacks.
Standard filtration is only effective for particles 10 microns or greater and therefore offers no solution to the problems of fine crystalline silica described hereinabove. Electrostatic precipitators which charge air-borne particles permitting them to agglomerate and precipitate into filters are minimally effective; however, the filters must be cleaned almost hourly in order to maintain their effectiveness. Further, they create a substantial amount of ozone which is believed to have critical effects on the health and safety of individuals, particularly in a closed room. The use of exhaust fans to exhaust the silica dust outside the facility may be effective, but it is only transferring the problem from inside the room to the exterior, and may face additional air quality control problems.
One solution which has been developed is to perform the greenware cleaning under water. The particles remain wet and do not become airborne. However, greenware cannot be wetted with aqueous solutions without damage thereto. Specifically, the wetted surface becomes glassy and fails to take up paint properly if the greenware is porcelain, and it melts is it is ceramic or stoneware. Therefore, under this prior art process, cleaning and scraping is performed on the ceramic after it is fired at a relatively low temperature for a short time, causing partial vitrification of the porcelain, ceramic or stoneware piece.
There are several drawbacks to this process however. First, the firing of the porcelain, ceramic or stoneware piece requires an extra firing step which is expensive and time consuming. Second, detail of the piece may be lost due to the increased difficulty in working with a partially vitrified piece. Additionally, the piece is more difficult to clean and it takes longer to clean, since the cleaning actually occurs while the piece is partially or fully submerged, and working under water is difficult. It is also messy since the water can splash or spill. Further, since the piece is partially fired, breaks and cracks cannot be repaired like they can when greenware is cleaned prior to firing.
Some craftspersons have used glycerin on the surface of greenware to minimize the escape of dust into the air. The use of glycerin, however, makes cleaning the greenware very difficult and in many cases, doesn't work at all. Most craftspersons believe that you cannot put any liquids on unfired porcelain without ruining the piece.
The present invention overcomes the deficiencies of methods of the prior art and provides a composition and method which makes the cleaning of greenware easier, faster, safer and more versatile than all of the prior art methods.